This present invention relates to methods and system for cleaning ink jet print heads utilized in an ink jet printer system. More particularly, the present invention relates to a method and system for hydrodynamically cleaning ink jet print heads.
Modem color printing relies heavily on ink jet printing techniques. The term xe2x80x9cink jetxe2x80x9d as utilized herein is intended to include all drop-on-demand or continuous ink jet propulsion systems including, but not limited to, thermal ink jet, piezoelectric, and continuous, which are well known in the printing arts. An ink jet printer produces images on a receiver by ejecting ink droplets onto the receiver medium, typically paper, in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
In this regard, xe2x80x9ccontinuousxe2x80x9d ink jet printers utilize electrostatic charging tunnels that are placed close to the point where ink droplets are ejected in the form of a stream. The electrostatic charging tunnels electrically charge selected ink droplets. The charged ink droplets are then deflected downstream by the presence of deflector plates that have a predetermined electric potential difference between them. A gutter can be utilized to intercept the charged ink droplets, while uncharged ink droplets are free to strike the receiver medium. Ink drops not utilized for printing are transferred to the gutter where they can be recycled. Continuous ink jet systems thus create a continuous stream of ink drops, generated by periodically perturbing an associated print head orifice with, for example, a piezoelectric transducer.
In the case of xe2x80x9con demandxe2x80x9d ink jet printers, a pressurization actuator is utilized to produce the ink jet droplet at every orifice. One of two types of actuators, either a heat actuator or piezoelectric actuator, may be utilized to produce the ink jet droplet. In the case of a heat actuator, a heater is placed at a convenient location to heat the ink. A quantity of ink will then phase change into a gaseous steam bubble, thereby raising the internal ink pressure sufficiently to permit an ink droplet to be expelled onto the receiver medium. In the case of piezoelectric actuators, a piezoelectric material possessing piezoelectric properties is utilized to produce an electric field when a mechanical stress is applied. The converse is also true. An applied electric field produces a mechanical stress in the material. Naturally occurring materials possessing such characteristics include quartz and tourmaline. The most commonly produced piezoelectric ceramics include lead zirconate titanate, barium titanate, lead titanate, and lead metaniobate.
Recently, a new type of continuous ink jet printer was disclosed. U.S. Pat. Nos. 6,079,821 and 6,234,620 to Chwalek et al., which describe a continuous ink jet printer in which on demand asymmetric heating of an ink jet causes selected drops to deflect. In one mode of operation, selected drops are deflected toward an image-receiving medium while the other drops are intercepted in a canopy-type gutter placed in close proximity (e.g., 3 mm) to the ink jet orifice plate.
Inks for high-speed ink jet printers, whether of the xe2x80x9ccontinuousxe2x80x9d or xe2x80x9cpiezoelectricxe2x80x9d type, must have a number of special characteristics. For example, the ink should incorporate a nondrying characteristic; so that drying of ink in the ink ejection chamber is hindered or slowed to such a state that by the occasional spitting of ink droplets, the cavities and corresponding orifices are kept open. The addition of glycol facilitates free flow of ink through the ink jet chamber.
Of course, the ink jet print head is exposed to the environment where printing occurs. Thus, the aforementioned orifices are exposed to many kinds of air born particulates. Particulate debris may accumulate on surfaces formed around the orifices and in the orifices and chambers themselves. The ink may combine with such particulate debris to form an interference that blocks the orifice or alters surface wetting, thereby inhibiting the proper formation of the ink droplet. The particulate debris should be cleaned from the surface and orifice to restore proper droplet formation. In the prior art, cleaning is commonly accomplished by brushing, wiping, spraying, vacuum suction, and/or spitting of ink through the orifice.
Thus, inks used in ink jet printers can be said to have the following problems: the inks tend to dry-out in and around the orifices resulting in clogging of the orifices; and the wiping of the orifice plate causes wear on the plate and wiper, the wiper itself producing particles that clog the orifice.
Ink jet print head cleaners are known. An ink jet print head cleaner is disclosed in U.S. Pat. No. 4,970,535 titled xe2x80x9cInk Jet Print Head Face Cleanerxe2x80x9d issued Nov. 13, 1990, in the name of James C. Oswald (the ""535 Patent). The ""535 Patent discloses an ink jet print head face cleaner that provides a controlled air passageway through an enclosure formed against the print head face. Air is directed through an inlet into a cavity in the enclosure. The air that enters the cavity is directed past ink jet apertures on the head face and exits via an outlet. A vacuum source is attached to the outlet to create a sub-atmospheric pressure in the cavity. A collection chamber and removable drawer are positioned below the outlet to facilitate disposal of removed ink. The technique uses heated air to remove the ink. Heated air is less effective for cleaning than a liquid solvent and can also damage fragile electronic circuitry that may be present on the print head face.
Other print head cleaning systems attempt to incorporate physical elements to clean debris from ink jet print heads. For example, a skip stroke wiping system is disclosed in U.S. Pat. No. 5,774,140 titled xe2x80x9cSkip Stroke Wiping System for Ink Jet Print Heads,xe2x80x9d issued Jun. 30, 1998, in the name of Kris M. English (the ""140 Patent). The ""140 Patent discloses a skip stroke wiping method for cleaning an ink jet print head and involves wiping and scraping steps. While the apparatus and method described in the ""140 Patent will remove debris, the harsh scraping and wiping steps can wear down the print head over time, thereby requiring a complicated wiping mechanism that is costly to replace if damaged.
U.S. Pat. No. 6,183,057 to Sharma et al. describes a cleaning assembly involving a removable gutter (not fixed) and a cup that sealingly engages the print head. Cleaning liquid supplied to the cup flows between a septum and the print head surface, thereby creating a zone of high shear. The cleaning liquid then exits via an outlet provided on the opposite side of the septum. This cup and septum arrangement cannot be utilized to clean the printer when the gutter is fixed.
Based on the foregoing, it can be appreciated that what is needed to efficiently clean an ink jet print head is a non-invasive print head cleaning method and system, one that involves the flow of fluids to remove debris and contaminants present on an ink jet print head, without damaging the print head itself. Such a method and system, if implemented, would avoid the aforementioned problems associated with present print head cleaning methods and systems, particularly those that involve heating techniques or complicated wiping mechanisms.
It is an object of the present invention to provide an ink jet printer having a cleaning assembly for cleaning a surface of an ink jet print head.
It is another object of the present invention to provide an ink jet printer having a cleaning assembly for cleaning a surface of an ink jet print head having a fixed type gutter.
It is another object of the present invention to provide a method and system for pumping a cleaning liquid across the print head surface to achieve cleaning of the surface and print head orifices.
It is yet another object of the present invention to remove used cleaning fluid from the print head, thereby cleaning contaminants from the surface of the print head and any associated print head parts, such as an orifice or orifice plate.
It is still another object of the present invention to provide a method and system for dislodging and removing contaminants from an ink jet print head and associated print head parts, including the gutter, utilizing a cleaning liquid that is pumped across the print head and simultaneously removed.
With the above objects in view, a cleaning assembly for use in an ink jet printer is disclosed. The ink jet printer includes a print head having a print head surface and one or more ink orifices disposed on the surface. The printer also includes a structural member that functions as a gutter for collecting ink, such that the gutter is disposed opposite the print head surface. The cleaning assembly is configured to clean contaminant from the print head surface.
According to an exemplary embodiment of the present invention, a self-cleaning printer system comprises a print head defining a plurality of ink channels disposed therein, wherein each ink channel terminates at an orifice. The print head also includes a surface thereon surrounding all the orifices. The print head is capable of jetting ink through the orifices. Ink jets are heated, causing ink drops to form and selectively deviate for printing. A receiver medium or a gutter can intercept the ink drops. In one method of operation, ink is selectively deflected onto a receiver medium (e.g., paper or transparency) supported by a platen disposed adjacent the print head, while the non-deflected ink drops are intercepted by a gutter.
Ink intercepted by the gutter can be recycled. Contaminants, such as oily film-like deposits or particulate matter, may reside on the print head surface thereby completely or partially obstructing the orifice. The oily film may, for example, be composed of grease. The particulate matter, on the other hand, may be composed of particles of dirt, dust, metal and/or encrustation of dried ink. The presence of contaminants interferes with the proper ejection of ink droplets from their respective orifices and therefore may give rise to undesirable image artifacts, such as banding. It is thus desirable to clean contaminants from the print head surface and orifices.
Therefore, a cleaning assembly is disposed relative to the surface and/or orifices for directing a flow of cleaning liquid along the surface and/or across the orifices, thereby cleaning contaminants therefrom. As described in detail herein, the cleaning assembly has an inflow channel appropriately angled to direct cleaning liquid at the orifices.
In another embodiment, cleaning liquid may be forced into the orifices and then out through an outlet provided in the print head. This back-flow enhances cleaning. In yet another embodiment, cleaning liquid may be supplied to the print head surface through a channel provided in the gutter. Thereafter, cleaning liquid can be directed to flow out of a cup via an outlet pipe, a channel in the gutter or through the orifices. In still another embodiment, ink jetting out of the orifices may be collected in a cup and swept away by cleaning liquid flowing into the cup. A pump for supplying cleaning liquid through the cup, print head or gutter is provided and provides suction. In addition, a filter can be used to filter particulate matter from the liquid for later disposal. In yet another embodiment, an ultrasonic transducer is used to enhance cleaning by energizing the cleaning liquid. In still another embodiment, cleaning liquid may carry gas bubbles to aid in cleaning of contaminant. The cleaning liquid may also be surged forward and backward by a piston device, thereby increasing cleaning efficiency.
An advantage of the present invention stems from the facts that fluids are non-invasively pumped across the print head in a manner that does not damage the print head.
Another advantage of the present invention lies in the ability of the channel to deliver fluids to the print head without damaging the print head surface.
A further advantage of the present invention stems from the fact that contaminants and debris can be removed from the print head and associated print head parts without the use of expensive and cumbersome heating techniques typical of many present prior art print head cleaning systems.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when read in association with the drawings depicted herein.